1. Field of the Invention
The present invention relates to a cowling of a motorcycle.
2. Description of the Related Art
There is known a motorcycle in which an engine unit is mounted on a central front lower part of a motorcycle body, and the engine unit and an exhaust expansion chamber constituting an exhaust device connected to the engine unit are covered with a cowling (see, for example, Japanese Patent No. 3046435 and Japanese Unexamined Patent Application Publication No. 2002-302082).
Another motorcycle is also known in which a plurality of exhaust pipes for guiding exhaust gas to an exhaust expansion chamber is connected to a multi-cylinder engine unit, an exhaust joint portion for joining the exhaust pipes is disposed in the exhaust pipes, and an exhaust throttle valve for varying the cross-sectional area of an exhaust path and an oxygen sensor for measuring the oxygen content in the exhaust gas are disposed between the exhaust joint portion and the exhaust expansion chamber.
However, when the exhaust expansion chamber is disposed at the rear portion of the exhaust throttle valve and the oxygen sensor, and the surrounding areas of these components are covered with a cowling, hot air heated by the exhaust pipes remains in the surrounding areas of the exhaust throttle valve and the oxygen sensor. In particular, the rear portion of the cowling is shaped so as to be blocked by the exhaust expansion chamber, and it is hence difficult for the hot air to come out of the cowling well. In addition, since an oil pan for storing high-temperature lubricating oil is disposed above the exhaust throttle valve and the oxygen sensor, the ambient temperature becomes high, which is inconvenient.
Therefore, since the temperature of the surrounding areas of the exhaust throttle valve and the oxygen sensor becomes significantly high, there is a fear of deteriorating the durability and reliability of these devices.